Removal of wax from hydrocarbon oil



Patented Mar. 31, 1936 UNITED STATES PATENT OFFICE Bernard Y. McCarty,Beacon, N. Y., and William E. Shelton, Fort Worth, Tex., assignors toThe Texas Company, New York, N. Y., a corporation of Delaware NoDrawing. Application June 8. 1934, Serial No. 729,802

3 Claim.

This invention-relates to the removal of wax from hydrocarbons and moreparticularly to an improved process for the removal of parafiin fromlubricating oil fractions derived from petroleum.

This application is a continuation-in-part of our co-pendingapplication, Serial No. 578,206, filed November 30, 1931, now Patent No.1,995,153, issued March 19, 1935, for Removal of wax from hydrocarbonoil.

The invention contemplates a process of dewaxing wax-containinglubricating oil fractions by filtration at low temperatures, wherein thewaxcontaining oil is mixed with a wax-precipitating liquid mediumcomposed of a solvent liquid or 1 mixture of solvent liquids which iscompletely miscible with, and exerts a substantially complete solventaction upon, the oil at the temperatures at which the wax constituentsare precipitated from the oil in solid form and which has substan- 20tially no solvent action on the solid hydrocarbons at such temperatures.The resulting mixture is then chilled to precipitate the solidhydrocarbons which are removed by filtration.

More specifically the invention contemplates mixing with lubricating oilfractions a wax-precipitating liquid medium composed of a mixture ofortho dichloro-benzene with either amyl gicohol, ethene-glycol-mono-butylegler, eth I heme, ro lene dichloride or ethylenedichlgngg, In some instances, ordinary commercial benzine may be used asin the case of mixtures with the ether compound.

The amyl alcohol referred to above may include the various isomers ofamyl alcohol, or mixtures 35 of them, such as Pentasol or the fusel oilof commerce. Other aliphatic alcohols, containing from four to sevencarbon atoms, including butyl and hexyl alcohols or their isomers may beemployed.

An object of this invention is to effect dewax- 40 ing ofparaflln-containing hydrocarbon oils with an improved type of solventliquid composed of a mixture of solvents having selective solventproperties between the oil and the wax constituents and which, inaddition, retains its selective 45 solvent properties at relatively lowtemperatures whereby the precipitation of the wax from the mixture,particularly in the case of mixtures with relatively viscous oils, iseffected in a more readily fllterable form. At the same time, a highyield of dewaxed oil is obtained.

A further object has been to develop a. solvent liquid which possessedthe foregoing properties at relatively low temperatures and which is, 65therefore, adaptable for the manuiacture of lubrlcating oils having pourtests of 20 F. and lower.

A selective solvent suitable for the foregoing dewaxing operation, andparticularly when composed of two or more organic solvents, must retainits homogeneity and its property of remaining completely miscible withthe liquid hydrocarbon constituents of the mineral oil at temperaturessubstantially well below F. Complete miscibility is necessary in orderto prevent separation of such liquid hydrocarbons from the solution.Such separated liquid hydrocarbons materially increase the viscosity ofthe solution thereby tending to reduce the filtering rate to a pointwhere the operation is not economical. In addition, the presence of thisseparated liquid gives rise to a condition which is productive uponfiltration of a wax cake containing substantial amounts of oil so thatthe maximum yield of dewaxed oil is not realized.

It is essential that such a solvent mixture remain completelyhomogeneous at these low temperatures and not exhibit any tendency forany of its components to separate from the mixture. Upon separation ofone of the components from the solvent mixture, the ratio of thecomponents remaining in the mixture is altered, thereby changing itsselective solvent properties so that the wax constituents will not becompletely precipitated and/or appreciable amounts of the liquidhydrocarbon may separate from the solution due to the resulting lack ofcomplete miscibility on the part of the solvent with the oil owing toits altered condition.

Extensive investigation has demonstrated that a solvent liquid orsolvent mixture satisfactory for use as a wax-precipitating medium inthe dewaxing of wax-containing hydrocarbon oils must possess, amongother things, low absolute viscosity and low viscosity temperaturecoeflicient, high oil solubility at low temperatures, low wax solubilityat low temperatures, low freezing point, and also possess the propertyof precipitating wax in a readily filterable condition.

Accordingly after investigating various solvent liquid mixtures, it hasbeen found that a mixture of ortho-dichloro-benzene and amyl alcohol,diethylene-glycol-monobutyl ether, propylene, or ethylene dichloride,possesses the foregoing combination of properties, thereby rendering itsuperior to the solvent liquids or liquid mixtures hitherto used in theart and, therefore, particularly well adapted as a wax-precipitatingmedium for use in the manufacture of low pour test parailln baselubricating oil. The relative proportion of these liquids to each other.as well as that or the resulting solvent mixture to the oil. may bevaried as desired, depending upon the nature of the oil undergoingtreatment.

Thus when dewaxing a lubricating distillate fraction, having a viscosityof around to Saybolt universal seconds or higher at 210' 1"., aboutthirty parts oi the oil may be mixed with about seventy parts of asolvent mixture composed of around 20% ortho-dichloro-benzene and about80% oi commercial grade amyl alcohol. The resulting mixture is thenchilled to about l0 F. or to a temperature corresponding substantiallyto the desired pour test of the resulting dewaxed oil, following whichit is subjected to filtration while still maintained in a cold conditionto separate the precipitated wax constituents. Advantageously filtrationmay be carried out in the presence of a finely divided comminutedfilter-aid material which may be added to and commingled with the coldmixture of oil, solvent and suspended wax crystals. After removal of thesolvent liquid from the filtrate, the resulting lubricating oil willhave a pour test of 0 F. or lower.

Similar results may be obtained. on the other hand, by mixing the oil inabout the same proportion with a solvent mixture composed of about 65%ortho-dichloro-benrene and about 35% of either ethylene or propylenedichloride. It is irequently desirable to employ a solvent liquidmixture in which the benzene is at least equal in volume to either theethylene or propylene dichloride.

While the use of the foregoing solvent liquid mixtures has beendescribed in connection with a lubricating distillate traction ofrelatively high viscosity, it is contemplated that mixtures of thesesolvent liquids may be equally well employed with oils or variousviscosity ranges. It is also contemplated that mixtures of these solventliquids are not necessarily restricted to dewaxing distillate fractionsbut may also be used in dewaxing various wax-bearing fractions ofmineral oil.

Obviously many modifications and variations aossaor of the invention, ashereinbeiore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. The process of dewaxiug wax-bearing oil which comprises mixing withthe oil a selective solvent liquid composed of ortho-dichlorobenzene andan aliphatic alcohol having the wax anti-solvent character and action ofcommercial amyl alcohol in such proportions that at temperatures ot theorder oi -10 F. the mixture has substantially complete solvent action onthe oil but substantially no solvent action on the wax, chilling themixture to precipitate the wax. separating the wax thus precipitated,and removing the solvent from the resulting dewaxed oil.

2. The process of dewaxing wax-bearing oil which comprises mixing withthe oil a selective solvent liquid composed of ortho-dichloro-benzeneand a liquid comprising commercial amyl alcohol in such proportions thatat temperatures of the order of -10 F. the mixture has substantiallycomplete solvent action on the oil but substantially no solvent actionon the wax, chilling the mixture to precipitate the wax, separating thewax thus precipitated, and removing the solvent from the resultingdewaxed oil.

3. The process of dewaxing wax-bearing oil which comprises mixing withthe oil a selective solvent liquid composed of ortho-dichloro-benzeneand commercial amyl alcohol in such proportions that at temperatures ofthe order 01' 10 F. the mixture has substantially complete solventaction on the oil but substantially no solvent action on the wax,chilling the mixture to precipitate the wax, filtering the cold mixturein the presence of a filter-aid material to remove the wax, and removingthe solvent from the resulting dewaxed filtrate.

